A 82-year-old celibate monk from Cambodia has HIV. So what is the cause? It turns out that his doctor was reusing syringes and this resulted in 272 people getting infected with HIV, including babies and children.

The World Health Organization warns that reusing syringes can also expose people to Ebola, malaria and other diseases. The organization wants countries to start using "smart syringes": syringes that disable themselves after one injection.

"Some have a metal clip that blocks the plunger and you cannot pull it back to give another injection. Some have a weak point, so if you try to pull it back, it breaks. And some have a device, like a spring, that automatically retracts the needle after the plunger hits the bottom of the barrel." says Dr. Selma Khamassi, head of the WHO team for injection safety.

The only problem is keeping it affordable in low-income countries. A normal syringe costs 3 to 4 cents whereas a smart one costs 4 to 8 cents. Once the demand for them increases, the price will probably decrease.

Why do people reuse the syringe? Cost is the first reason. Secondly, some think that by changing the needle tip on the part that holds the medicine, they remain safe, which is not the case. Also, low-paid health workers reuse syringes to get an extra income by giving injections outside of their hospital. But it also happens in wealthy countries says Khassima, because of ignorance, laziness, lack of equipment or even greed.